Even when using USB4 I still haven't seen an ssd case that can use all that bandwidth.
Use case is video editing and maybe even egpu for Blender.
It is reserved.
"Thunderbolt 4 has a maximum bandwidth of 40 Gb/s. However, this is a bit misleading because not all of that bandwidth can be used for data transfer. Approximately 8 Gbp/s can only be used for video, leaving 32 Gb/s for non-video data (PCIe 3.0: 4 lanes x 8 Gb/s). Further accounting for PCIe 8b/10b encoding and TB4's own overhead, you arrive at a peak data throughput of approximately 22 Gb/s. Not 40 Gb/s but not slow either."
See this other comment of mine: